Field
The present specification generally relates to methods for forming vias in glass substrates and, more specifically, to methods for forming vias in glass substrates by laser drilling and acid etching.
Technical Background
An interposer may be used as an electrical interface in an electronic device to spread an electrical connection to a wider pitch or to reroute a connection to a different connection. Typically, many thousands of vias (i.e., holes) are formed in the substrate of the interposer, which are subsequently filled with electrically conductive material and further processed in order to interface electrical connections. Interposers may be formed from a variety of materials, such as from silicon, fiber reinforced polymer (“FRP”), and glass.
FRP interposers may suffer from a variety of drawbacks. For example, cylindrical vias may be formed in FRP interposers by drilling with undesirably expensive fine drill bits. Such drill bits may wander on the surface of the substrate, thereby limiting hole diameter and pitch. Furthermore, the coefficient of thermal expansion (“CTE”) of FRP interposers may be about five times greater than that of silicon, resulting in an undesirable thermal mismatch between silicon chips and FRP interposers. Moreover, FRP interposers tend to warp during processing, leading to difficulties with adhesion and bonding.
Glass interposers offer an attractive alternative to FRP interposers for a variety of reasons, such as the similarity of the CTE of glass to the CTE of silicon and the low cost of glass, among others. However, it may be difficult to form vias in glass interposers using conventional methods, such as drilling, which is not a practical technique for manufacturing glass interposers with vias.
Accordingly, a need exists for methods for forming vias in glass substrates.